hashtable doesnt read alphabet letter?

dim items3() as string
 Dim arrList As New ArrayList(items3)

        'use a hashtable to create a unique list
        Dim ht As New Hashtable()

            For Each item As Integer In arrList
                'set a key in the hashtable for our arraylist value - leaving the hashtable value empty
                ht.Item(item) = Nothing


for some reason when one of my array value is 111A, it crashed. Can't hash read character?
if so how do i fix this. thanks